Radio receiving system



June 4, 1929:, F. A, KOLSTER 1,716,35

RADIO RECEIVING SYSTEM Filed March 9, 1927 INVENTOR fi'eder/ck A. A o/sfer m, A TTORNE YS Patented June 4, 1929.

ATET' OFFICE.

FREDERICK A. KOLSTER, OF PALO ALTO, CALIFORNIA, ASSIGNOR TO FEDERAL TELE- GRAPH COMPANY, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF CALI- FORNIA.

' RADIO nEcEIvmG SYSTEM.

Application filed March 9, 1927. serial-no. 173,812.

This invention relates generally to system and method of receiving signal energy of carrier frequency. It has special application to receiving systems employing a plurality of electron relays for repeating and amplifying signal energy.

It is an object of this invention to devise a radio receiving system and method which will minimize static disturbances and which will give a high degree of selectivity.

It is a further object of this invention to devise a radio receiving system and method which will'incorporate the idea of energizing an electron relay from a source of alternating current having a frequency above audibility, as disclosed in my co-pending application No. 63,861 filed October 21, 1925.

It is another object of this invention to devise a novel radio receiving system and method which will incorporate avnumber of electron relays coupled together in cascade and which are operated in such a manner that a side band frequency selected from "a preceding relay is modulated in a succeeding relay.

Further objects of this invention will appear from the following description in which I have set forth the preferred embodiment of my invention. It is to be understood that the appended claims are to be accorded a range of equivalents consistent with the stateof the prior art. 1

Referring to the drawing: The single circuit diagram illustrates one embodiment of this system and method.

The invention may be explained in general terms as comprising a plurality of electron relays connected together in cascade. Each of the relays is energized from a local source of alternating current having a frequency above audibility and which differs from the frequency of the signals to be received. Filter devices are employed for coupling together the successive electron relays and these filter devices are tuned so as to select aside band frequency from the preceding relay for impressing the same upon the input of a succeeding relay. In practice the side band frequency which is selected out is the differential frequency, which in the last relay stage may be of audible frequency.

Thus referring to the drawing thereis shown a plurality of electron relays 10, 11, 12, and 13, the relays-10, lland 12 being employed as amplifiers while the relay 13 is employed as a detector or integrating device.-

Each of the relays is preferably of the three element type comprising the usual grid or control element 14, anode or plate 16 and electron emission element, or filament 17. The

input circuit of the first relay 10 is coupled to a suitable'source of signal energy of carrier frequency, such as a loop antenna 18 which' may be'tuned by means of a variable condenser 19. The successive'relay stages are coupled together 'by means of tuned circuits or filter devices 20, 21 and 22 which may con- 51st of ordinary coupling transformers hav ing their secondary windings tuned by means of variable condensers 23.

In order to operate each of the relays as a modulator, each relay is associated with a local oscillator which produces alternating current at a frequency difl'ering from'the carrier frequency of the signals being received. In practice it is also desirable to energize the electron relays with the current from this oscillator in a manner which I have described in my co-pending application No. 63,861 referred to above. Thus there is shown a local oscillator 26 preferably operating at a he I quency above audibility and which is coupled to supply oscillatory energy to the output circuits of the "respective relays as by means of a plurality of coupling transformers 2 7. This oscillatory current also serves as a convenient means for energizing the filaments 17 which have also been shown as coupled to the secondary of transformers 27 as by means of variable condensers 28. As the relay 13 is being operated as a detector, it is provided with the usual grid condenser 29 and grid leak 30. The output of detector relay 13 supplies a suitable translator which has been indicated in the form of telephone receivers 31.

In operating the system which has been decy is-selectedout y proper adjustment of v filter 20 and is imposed upon the input of relay 11. As relay 11 is also energized from the oscillator, frequency, this first beat frequency will be modulated a second time in re lay 11 to produce another set of side band frequencies. Filter 21 is then tuned to separate out the differential frequency produced by this second modulation and this second differential frequency is imposed upon relay 12. In relay 12 the second differential frequency is modulated by the local oscillator frequency to produce another differential frequency which is separated out by filter 22 and imposed upon the detector 13. In this last relay the differential frequency separated out by filter 22 is modulated to produce a frequency which is translated by the receivers 31.

By properly selecting the frequency of the local oscillator 26 with the frequency of the incoming signals. the difierential fremiency received by translator 31 is made an audible tone for the reception of telegraphic signals. In other words when filters 20, Q1 and 22- are all adjusted so as to separate out the ditl'erential frequencies produced in a preceding amplifier for impressing upon a succeeding am plifier, a definite relation will exist between the frequency of the incoming frequency, the frequency of the oscillator and the tone frequency of the energy received by the translator 31. This relationship may be expressed by the following simple equation Where n n and n, are the differential frequencies to be produced in the outputs of re lays 10, 11 and 12 respectively.

Now assuming the following values for n,, t and N:

N 100,000 cycles =received frequency.

t 1,000 cycles signal or tone frequency desired. N =4 or the number of tuned circuits. Then n 100,000 24,7 75,250 cycles. n 75,250 24,750 ='50,500 cycles. n 50,500 24,750=25,7 50 cycles.

t 25,750 24,750 1,000 cycles. Thus in the particular system disclosed, if the antenna is tuned to 100,000 cycles or 3000 meters, filters 20, 21 and 22 tuned to 3990,

50-40 and 11,050 meters respectively, and the oscillator tuned to 1000 meters, atone fre quency of 1000 cycles will be produced in the translator 31.

Due to the fact that each relay stage is tuned to a frequency differing from the received frequency and no two stages are tuned the same, the system is highly selective. Furthermore disturbances due to static and strays are minimized as the detuned coupling transformers are not susceptible to shock excitation.

It is obvious that the detector relay 13 may be energized from the usual source of direct current if it is not desired to modulate after the last amplifier relay. In this case if the frequency separated out by transformer 22 is well above audibility. the system may be used for the reception of telephonic signals.

I claim i 1. A method of repeating signal energy of carrier'frequcncy characterized by the use of a plurality of electron relay amplifiers connected together incascade, each relay having an anode connected to its output circuit, said method comprising maintaining operative anode potentials for the respective relays with periodically varying current, the frequency of said current being above audibility and serving to modulate repeated fro.- quencies;

2. The method of repeating signal energy characterized by the use of a plurality of electron relay amplifiers connected together in cascade, each relay having an anode included in its output circuit, said method comprising maintainin operative anode potentials for the respective relays With periodically varying current whereby the energy repeated by each amplifier is modulated by a given frequency, and selecting a resulting frequency from each preceding amplifier and impress ing thesame upon a succeeding amplifier.

3. The method of repeating signal energy characterized by the use of a plurality of electron relay amplifiers connected together in cascade, each relay having an anode associated with its input circuit, an electron relay detector supplied from the last amplifier stage and a translator suppliedby the detector, said method comprising maintaining operative anode potentials upon the respective amplifier relays from a source of periodically varying current having a frequency above audibility whereby the signal energy is modulated in each amplifier, selecting out the differential frequencv from each preceding amplifier and impressing the same upon a succeeding amplifier, selecting out the differential frequency from the last amplifier and impressing the same upon the detector, and modulating the energyrepeated in the detector to produce a signal of audible frequency in thetranslator.

1. In a signalling system, a plurality of electron relay amplifiers connected together in cascade, each of said relays having an anode associated with its output circuit, filter means intercoupling said amplifiers, means for coupling the first amplifier of the series to a source of signal energy of carrier frequency, local oscillator means for generating current havin a frequency above audibility but differing fi'om the carrier frequency, and means for maintaining operative anode potentials on said relays With current supplied from said oscillator means whereby the energy repeated by each amplifier is modulated by the frequency of the oscillator, said filter means being tuned to transfer only one re- 1 sulting frequency from a preceding amplifier to a succeeding amplifier.

5. In a signalling system, a plurality of electron relays connected together in cascade and forming a multistage amplifier and a detector, said relays each having an anode associated with its output circuit, means for coupling the firstrelay, of the series to a source of signal energy of carrier frequency, local oscillator means for generating supersonic frequency current differing from said carrier frequency, means for maintaining operative anode potentials on said relays with currents from said oscillator means whereby the energy repeated by each relay is modulated b the oscillator frequency, and filter means or coupling together each relay, eachfilter being tuned to transfer only resulting frequency to a successive relay.

and electron emission elements of each relay with current from said oscillator whereby the energy repeated by each relay is modulated by the oscillator frequency, and filter means for coupling together each relay, each filter being tuned to transfer only the differential beat frequency to a successive relay.

7. In a signaling system, a plurality of electron relays connected together in cascade, means for effecting a frequency change for currents repeated in each relay, and filter means imposed between each relay and associated with the last relay of the series, the filter means associated with the output and input circuits of any one relay being tuned to pass different frequencies whereby the frequency separated by the output is different from the frequency imposed upon the input circuit of the same.

In testimony whereof, I have hereunto set my hand.

FREDERICK A, KOLSTER. 

